Methods and devices for treatment of obstructive sleep apnea

ABSTRACT

A pharyngeal retractor device and implantation methods are provided for use in the treatment of obstructive sleep apnea. The device includes a retracting element and a tissue engaging element that promotes tissue ingrowth around or onto the retracting element. The device is implanted in tissue space beneath the pharyngeal wall to alter the shape of the wall. The device may be implanted through the oral cavity alone or by using a trocar or a hand-held delivery system to deliver the device through the pharyngeal wall. Alternatively, the device may be implanted using an open, direct visualization approach from the side of a patient&#39;s neck.

FIELD OF THE INVENTION

The present invention relates generally to the surgical treatment of obstructive sleep apnea, and more particularly, to the use of implants to prevent pharyngeal wall collapse or to provide altered airway geometries to prevent possible airway obstruction during sleep.

BACKGROUND OF THE INVENTION

Several forms of sleep apnea have been identified. Obstructive sleep apnea (OSA) is caused by a blockage of the airway, usually when the soft tissue in the throat collapses and closes during sleep. Less common forms of sleep apnea include central sleep apnea (CSA), wherein the airway is not blocked but the brain fails to signal the muscles to breathe, and mixed apnea which, as the name implies, is a combination of OSA and CSA.

As shown in FIG. 1 a, an air passage 140 a of a patient 101 a is open while the patient is in the awake state. The soft tissue components, including the soft palate 130 a and the pharyngeal walls 132 a of the air passage are supported by the underlying musculature to maintain the passageway in the open condition. During an obstructive sleep apnea event, illustrated in FIG. 1 b, the air passage 140 b of a patient 101 b is partially or completely blocked by surrounding soft tissue 130 b, 132 b, which has collapsed due to the relaxation of the supporting musculature and has been displaced during sleep by gravity or other forces.

With each apnea event, the brain briefly arouses the sleeping person in order to resume breathing, but sleep is consequently extremely fragmented and of poor quality. Untreated, sleep apnea can cause high blood pressure, cardiovascular disease, memory problems, weight gain, impotency, and headaches. Moreover, untreated sleep apnea may be responsible for job impairment, motor vehicle crashes, and marital discord.

According to the National Institutes of Health, sleep apnea is very common, as common as adult diabetes, and affects more than twelve million Americans. The factors that increase the risk of having OSA include being male, overweight, and over the age of forty, but sleep apnea can strike anyone at any age, even children. Because of the lack of awareness by the public and healthcare professionals, the vast majority of patients remain undiagnosed and therefore untreated, despite the fact that this serious disorder can have significant consequences.

Attempts to provide an effective treatment for obstructive sleep apnea have yielded unsatisfactory results. For example, electrical stimulation of the soft palate has been suggested to treat snoring and obstructive sleep apnea. Such a teaching is found in Schwartz et al., “Effects of electrical stimulation to the soft palate on snoring and obstructive sleep apnea,” J. Prosthetic Dentistry, pp. 273-281 (1996). Devices to apply electrical stimulation are described in U.S. Pat. Nos. 5,284,161 and 5,792,067. Electrical stimulation to treat sleep apnea is also discussed in Wiltfang et al., “First results on daytime submandibular electrostimulation of suprahyoidal muscles to prevent night-time hypopharyngeal collapse in obstructive sleep apnea syndrome,” International Journal of Oral & Maxillofacial Surgery, pp. 21-25 (1999). Such devices are appliances requiring patient adherence to a regimen of use as well as subjecting the patient to discomfort during sleep and repeated arousals during deep sleep.

Continuous Positive Airway Pressure (CPAP) has recently been adopted as a useful, albeit cumbersome, means of preventing sleep apnea. CPAP delivers air into the airway through a specially designed nasal mask or pillows. The mask does not breathe for the patient; the flow of air creates enough pressure when the patient inhales to keep the airway open. In effect, a pneumatic splint is formed in the airway. CPAP is considered the most effective non-surgical treatment for the alleviation of snoring and obstructive sleep apnea. Compliance, however, is only 50%, as patients complain about discomfort from the mask, hoses, etc. and that the equipment requires maintenance. Additionally, patients complain of discomfort such as bloating, nasal drying, and dry eyes.

Surgical treatments have also been employed. One such treatment is uvulopalatopharyngoplasty (UPPP). UPPP is discussed, for example, in Harries et al., “The surgical treatment of snoring,” Journal of Laryngology and Otology, pp. 1105-1106 (1996), which describes removal of up to 1.5 cm of the soft palate. The use of UPPP in the treatment of snoring is assessed in Cole et al., “Snoring: A review and a Reassessment,” Journal of Otolaryngology, pp. 303-306 (1995). In that procedure, about 2 cm of the trailing edge of the soft palate is removed through the use of a scalpel, laser or other surgical instrument, thereby reducing the tendency of the soft palate to flutter between the tongue and the pharyngeal wall of the throat. The procedure is frequently effective to alleviate snoring but has demonstrated limited effectiveness in moderate or severe apnea. The procedure is painful and frequently results in undesirable side effects. In particular, the reduction of the soft palate compromises the ability of the soft palate to seal off nasal passages during swallowing and speech. In an estimated 25% of uvulopalatopharyngoplasty patients, fluid escapes from the mouth into the nose while drinking.

Uvulopalatopharyngoplasty (UPPP) may involve lasting discomfort. For example, scar tissue on the soft palate may present a continuing irritant to the patient. In addition, UPPP is not reversible and may induce adverse side effects not justified by the benefits of the surgery. Furthermore, UPPP is targeted to the correction of deficiencies associated with the palate only and does not address issues associated with the collapse of the tongue and lateral pharyngeal walls.

Radiofrequency ablation of the soft palate, or Somnoplasty^(SM), is similar in concept to the Laser Assisted Uvulopalotopharyngoplasty (LAUP), although a different energy source is used, and thermal lesions are produced within the tissues, rather than using a laser to ablate the tissue surface. For that reason, radiofrequency ablation appears to be growing in popularity as an alternative to LAUP. The Somnoplasty^(SM) device is approved by the U.S. Food and Drug Administration (FDA) for radiofrequency ablation of palatal tissues for simple snoring and radiofrequency ablation of the base of the tongue for OSA. In some situations, radiofrequency ablation of the soft palate and base of tongue are performed together as a multi-level procedure. To date, the treatments alone or in combination have failed to provide relief to more than 50% of patients.

Another device intended to treat snoring or obstructive sleep apnea is comprised of several braided PET cylinders that are implanted to make the tissues of the tongue or uvula more rigid and less prone to deflection against the pharyngeal wall. The Pilla™ Palatal Implant System, marketed by Restore Medical of St Paul, Minn., is an implantable device that has been cleared by the FDA 510(k) process. The device is a cylindrical-shaped segment of braided polyester filaments that is permanently implanted submucosally in the soft palate. The labeled indication of the device is as follows: “The Pillar™ Palatal Implant System is intended for the reduction of the incidence of airway obstructions in patients suffering from mild to moderate OSA (obstructive sleep apnea).” The device has been associated with a number of adverse side effects, including extrusion, infection, and patient discomfort.

The Repose™ device, marketed by Influent Medical LLC of Concord, N.H., involves the use of a titanium screw that is inserted into the posterior aspect of the mandible at the floor of the mouth. A loop of suture is passed through the tongue base and attached to the mandibular bone screw. The Repose™ procedure achieves a suspension or hammock of the tongue base making it less likely for the base of the tongue to collapse against the posterior pharyngeal wall during sleep. The reported duration of beneficial effects afforded by the implant is less than a year. Due to the high activity of the tongue during wakefulness, the suture component of this device has been shown in some cases to act as a “cheese cutter” to the tongue, causing device failure and requiring subsequent removal.

Magnets have also been considered as implants for the treatment of obstructive sleep apnea. These devices are currently being evaluated in clinical trials. One serious complication than can potentially occur with these implants is implant migration or flipping of the magnets which can cause acute airway closure.

In summary, electrical stimulation of the musculature within the airway is ineffective since it arouses the patient from deep sleep. CPAP effectively manages OSA but has a very low patient compliance (less than 50% of patients continue the treatment). Surgical techniques and implants have also been evaluated, yet still do not provide a satisfactory and lasting solution. No one device seems capable of treating the multi-causal problem of obstructive sleep apnea. What is needed are methods and devices that reduce the burden of managing obstructive sleep apnea through a minimally invasive approach that provides long term and effective results. Ideally, the treatment should be adjustable and removable if necessary. The inventions described herein provide such treatments that offer long-term relief of OSA.

SUMMARY OF THE INVENTION

The present invention is directed to systems and methods for treating obstructive sleep apnea. One embodiment of the invention is a method for surgically treating obstructive sleep apnea, comprising the step of implanting a device into tissue space located beneath a pharyngeal wall to alter a shape of the pharyngeal wall. In one embodiment, the device retracts or alters the shape of the pharyngeal wall to resist collapse. In another embodiment, the device alters the geometry of the airway to prevent complete obstruction of the pharyngeal tissues during sleep.

The device is a retractor that has a self-supporting tissue engaging element that controls the position of the soft tissues beneath the pharyngeal wall during sleep and allows for tissue ingrowth. The tissue engaging element may, for example, be a biocompatible mesh or other suitable porous fabric. The tissue engaging element may be made through typical processing means including, but not limited to, fiber knitting, weaving, braiding, non-woven production, expansion methods (such as ePTFE) or perforation of film type products, melt blowing, extrusion, carding, or injection molding. The retractor is generally of a “sheet like” or planar shape, with the width, length and thickness dimensions of the retractor typically not equal.

The retractor may be introduced orally and implanted through the pharyngeal wall into the tissue beneath the pharyngeal wall. The retractor may alternatively be introduced through a side of a patient's neck. The retractor is placed within the soft tissues of the neck, either within tissue planes or crossing them, as deemed appropriate by the surgeon to produce sufficient retraction or alteration of the lumen of the affected region of the airway.

One embodiment of the invention is a device for altering a shape of a pharyngeal wall by implantation of the device in tissue beneath the pharyngeal wall. The device comprises a retracting element having a constrained configuration and an unconstrained configuration different from the constrained configuration, and a tissue engaging element connected to the retracting element, the tissue engaging element adapted for engaging the tissue beneath the pharyngeal wall. A shape of the pharyngeal wall is altered when the retracting element reverts from the constrained configuration to the unconstrained configuration.

Another embodiment of the invention is a method for surgically treating obstructive sleep apnea. The method includes the steps of delivering an implantable device into tissue located beneath a pharyngeal wall, and engaging the tissue beneath the pharyngeal wall with the implantable device to alter a shape of the pharyngeal wall.

The invention is further embodied by a system for treating obstructive sleep apnea by altering a shape of a pharyngeal wall. The system comprises an implantable device including a tissue engaging element and a retracting element, and a hand-held delivery system comprising a hand-piece, an actuating lever moveably connected to the hand-piece, a shaft extending distally from the hand-piece, a housing disposed at a distal end of the shaft for storing at least one implantable device, and a deployment device activatable by the lever for deploying the implantable device through the pharyngeal wall into tissue space located beneath the pharyngeal wall so as to alter a shape of the pharyngeal wall.

Another embodiment of the invention is a device for retracting a pharyngeal wall. The device includes an elongate fibrous member having a central portion for engagement with the pharyngeal wall, and having first and second retracting portions extending from the central portion, each of the first and second retracting portions having features for engaging tissue in the neck and exerting a tensile retraction force on the central portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a and 1 b are schematic cross-sectional representations of a patient's upper airway.

FIG. 2 is a schematic cross-sectional representation of a patient's upper airway.

FIG. 3 a is a cross-sectional view of a pharyngeal wall showing several superimposed states of the wall.

FIG. 3 b is a cross-sectional view of a pharyngeal wall showing two pharyngeal retractors implanted according to one embodiment of the invention.

FIG. 4 is a plan view of a trocar according to one embodiment of the invention.

FIG. 5 is a plan view of a pharyngeal retractor implant system according to another embodiment of the invention.

FIGS. 6 a-6 f are views of several pharyngeal retractors according to various embodiments of the invention.

FIG. 7 is a schematic representation of a patient's upper airway showing a pharyngeal retractor implanted according to one embodiment of the invention.

FIG. 8 is a schematic representation of a patient's upper airway showing a pharyngeal retractor implanted according to one embodiment of the invention.

FIG. 9 is a schematic transverse cross-section of a patient's head at a level below the temporal styloid process, showing one embodiment of the invention.

FIG. 10 is a schematic representation of a patient's head showing a pharyngeal retractor implantation method according to one embodiment of the invention.

FIG. 11 a is a schematic cross-sectional representation of a patient's upper airway showing two pharyngeal retractors during an implantation process according to one embodiment of the invention.

FIG. 11 b is a schematic cross-sectional representation of a patient's upper airway showing the two pharyngeal retractors of FIG. 11 a after implantation.

FIG. 12 a is a schematic cross-sectional representation of a patient's upper airway showing two pharyngeal retractors during an implantation process according to another embodiment of the invention.

FIG. 12 b is a schematic cross-sectional representation of a patient's upper airway showing the two pharyngeal retractors of FIG. 12 a after implantation.

FIG. 13 is a cross-sectional representation of a patient's upper airway showing a pharyngeal retractor according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a device and method of implantation that can be used to treat obstructive sleep apnea. The device can be implanted into tissue beneath the pharyngeal wall using several implantation methods described herein. The term “beneath the pharyngeal wall” refers to a space beneath the pharyngeal wall that does not exist naturally but is formed during the implantation step. The newly formed space allows the device to be implanted next to the back of the pharyngeal wall (the side that does not face the airway) and against the prevertebral fascia and musculature such as the longus capitus muscles. The device, referred to herein as a retractor or simply as the “device,” may include a flexible backing or arch-shaped retracting element attached to a tissue engaging element. The device is used to alter a characteristic of the pharyngeal wall. For example, the device may provide additional retraction means on the lateral pharyngeal walls or maintain an altered shape of the airway. The device of the invention provides retraction or support of the pharyngeal walls to allow air to flow past any obstruction that may be apparent if the pharyngeal walls are collapsed. It may also be used to change the shape of the pharyngeal airway.

FIG. 2 illustrates a cross-section of a patient's head with anatomical structures such as the nasal sinuses (N), bone (B) of the hard palate (HP), soft palate (SP), mouth (M), tongue (T), trachea (TR) epiglottis (EP), esophagus (ES) and posterior pharyngeal wall (PPW). The lateral pharyngeal walls (not shown in this illustration) are, as the name implies, lateral to the posterior pharyngeal wall. According to imaging studies on CPAP users described by Schwab et al., “Upper airway and soft tissue changes induced by CPAP in normal subjects,” Am. J. Respir. Crit. Care Med., Vol 154, No. 4, October 1996, 1106-1116, the lateral pharyngeal walls are more “compliant” than the soft palate and tongue. Those studies provide evidence that the lateral pharyngeal walls play an important role in mediating upper airway caliber. In certain disclosed embodiments, the intent of the implantable devices described herein is to retract the pharyngeal walls laterally. The lateral retraction serves to prevent collapse of these soft tissue structures and to maintain an airway for the patient, particularly when the diaphragm descends during inhalation and causes excessive negative pressure that might act to collapse the pharyngeal walls. In certain other disclosed embodiments, the intent of the implantable device is to provide altered geometries of the airway during inhalation that are unable to occlude due to mismatched geometries between the mating tissues, more particularly the base of the tongue and the posterior and or lateral pharyngeal walls.

FIG. 3 a illustrates a cross-section of the pharynx at the oropharyngeal level, including the posterior pharyngeal wall (PPW) and lateral pharyngeal walls (LPW). The oropharynx is shown in solid lines in its distended (retracted) state, and is shown in dashed lines in a normal relaxed state and in a partially collapsed state. As shown in FIG. 3 b, a pair of implantable devices 301 a, 301 b in accordance with the invention causes the left (LLPW) and right (RLPW) lateral walls of the pharynx to resist the negative pressure produced by the descending diaphragm, thereby keeping the airway open. Subsequent tissue engagement with the implantable device and tissue ingrowth 302 into the device serve to secure the mesh strip, and therefore, to stabilize the retracted state.

One embodiment of the invention is an implantable device that is releasably attached to at least one trocar. FIG. 4 illustrates a trocar 400 having a distal end 401 and a handle 402 on the proximal end. The distal end 401, with the implantable device attached, is passed through the pharyngeal wall and into the tissue underneath the pharyngeal wall. The implantable device is then placed in the formed space beneath the pharyngeal wall.

The trocar 400 may optionally have a Doppler probe (not shown) that allows detection of blood flow in any arterial structures located near the target tissues. The probe may be embedded within the distal tip 401 so as to help navigate the tissue and avoid damaging blood vessels, particularly when an approach is utilized whereby the implantable device is installed across multiple tissue planes within the affected regions of the neck.

In addition to the minimally invasive approach using a trocar, the device may alternatively be placed beneath the pharyngeal wall using an open, direct approach to the pharyngeal wall from the side of a patient's neck. A single device or more than one of the devices can be used to treat the patient.

FIG. 5 illustrates an exemplary attachment of a mesh device 500 to the trocar 400. The mesh device 500 is fixed to a proximal end of a plastic trocar sleeve 502 that covers the distal end of the trocar. The fixation of the mesh to the end of the plastic trocar sleeve can be achieved through the use of wrapping, welding, gluing, tying, clips or other suitable means. In one embodiment, the device 500 is a mesh made from polypropylene or another porous biocompatible material selected for its tissue engaging properties.

In the embodiment shown, the implantable device 500 is covered by a protective sheath 501. Polymers such as expanded polytetrafluoroethylene (ePTFE), polyethylene terephalate (PET), PVDF, polyesters, polyolefins, silicones or polyurethanes are utilized in the construction of the protective sheath. The materials and construction techniques of the protective sheath are chosen so as to minimize friction and engagement of the sheath with surrounding tissue. The purpose of the protective sheath 501 is to minimize tissue drag on the implantable device during insertion and to prevent any abrasion or irritation of non-target tissues during placement of the device.

In use, the distal end 401 (FIG. 4) of the trocar penetrates the pharyngeal wall at or near a lateral or posterior portion of the wall. If necessary, the insertion of the trocar may be facilitated through the use of an incision made just prior to the implantation step. The site of incision and orientation of the device will be determined by the surgeon and will be dependent on the individual patient anatomy and the site of pharyngeal collapse. Alternatively, the trocar 400 may have a sharpened edge at its distal end 401 for piercing the mucosal surface of the pharyngeal wall. The trocar is then used to pass the mesh device 500 through the pharyngeal wall and to deposit the device in the tissue beneath the pharyngeal wall. In one embodiment, after penetrating the pharyngeal wall and passing through the tissue beneath the pharyngeal wall, the trocar tip is passed through the pharyngeal wall again at a second location, passing from underneath the wall to within the airway. The mesh is then drawn through the tissue using the plastic trocar sleeve, with the protective sheath surrounding the mesh to protect the tissue. The plastic trocar sleeve and the protective sheath are then removed. If the pharyngeal retractor is longer than necessary, it is trimmed to length while under slight tension to reduce the length that remains within the pharyngeal wall. The incisions in the pharyngeal wall are then closed with suture, clips, or biocompatible tissue adhesive.

FIG. 6 a illustrates one embodiment of an implantable device according to the invention. The device comprises a tissue engaging element shown in FIG. 6 a as a length of mesh 600. In the embodiment of FIG. 6 a, no other material is attached or associated with the mesh. The tissue engaging element is implantable into the space beneath the pharyngeal wall. The element is constructed to frictionally or otherwise engage surrounding tissue upon implantation, and to thereby resist movement after placement within the tissue.

The biocompatible tissue engaging element 600 is further receptive to tissue ingrowth in the form of scar tissue that embeds during healing and becomes integrated with the mesh. That scar tissue reinforces the overall tissue mass in which the tissue engaging element is implanted. The element may encourage structural ingrowth of surrounding tissue, and may also encourage cellular ingrowth of tissue.

Many medical textile designs are known to those skilled in the art of making mesh, fabrics, non-wovens, etc. for hernia repair. Medical textile products are based on fabrics, of which there are four types: woven, knitted, braided, and nonwoven. The first three of these are made from yarns, whereas the fourth can be made directly from fibers, or even from polymers such as Gore-Tex®-based products or electrostatically spun materials from polyurethane. There is, therefore, a hierarchy of structure: the performance of the final textile product is affected by the properties of polymers whose structures are modified at between two and four different levels of organization.

Of the many different types of polymers, only a few can be made into useful fibers. This is because a polymer must meet certain requirements before it can be successfully and efficiently converted into a fibrous product. For example, the polymer chains should be linear, long, and flexible. Side groups of the polymers should be simple, small, or polar. Polymers should be dissolvable or meltable for extrusion. Chains should be capable of being oriented and crystallized.

Common fiber-forming polymers include cellulosics (linen, cotton, rayon, acetate), proteins (wool, silk), polyamides, polyester (PET), olefins, vinyls, acrylics, polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), aramids (Kevlar, Nomex), and polyurethanes (Lycra, Pellethane, Biomer). Each of these materials is unique in chemical structure and potential properties. For example, among the polyurethanes is an elastomeric material with high elongation and elastic recovery, whose properties nearly match those of elastin tissue fibers. This material—when extruded into fiber, fibrillar, or fabric form—derives its high elongation and elasticity from alternating patterns of crystalline hard units and noncrystalline soft units.

Although several of the materials mentioned above are used in traditional textile as well as medical applications, various polymeric materials—both absorbable and nonabsorbable—have been developed specifically for use in medical products.

The reactivity of tissues in contact with fibrous structures varies among materials and is governed by both chemical and physical characteristics. Absorbable materials typically excite greater tissue reaction, a result of the nature of the absorption process itself. Among the available materials, some are absorbed faster (e.g., polyglycolic acid, polyglactin acid) and others more slowly (e.g., polyglyconate). Semiabsorbable materials such as cotton and silk generally cause less reaction, although the tissue response may continue for an extended time. Nonabsorbable materials (e.g., nylon, polyester, polypropylene) tend to be inert and to provoke the least reaction. To minimize tissue reaction, the use of catalysts and additives is carefully controlled in medical-grade products.

As discussed, of the many types of polymers, only a few can be made into useful fibers that can then be converted into medical textile products. To make fibers, polymers are extruded by wet, dry, or melt spinning and then processed to obtain the desired texture, shape, and size. Through careful control of morphology, fibers can be manufactured with a range of mechanical properties. Tensile strength can vary from textile values (values needed for use in typical textile products such as apparel) of 2-6 g/d (gram/denier) up to industrial values (values typical of industrial products such as tire cords or belts) of 6-10 g/d. For high-performance applications, such as body armor or structural composites, novel spinning techniques can produce fibers with strengths approaching 30 g/d. Likewise, breaking extension can be varied over a broad range, from 10-40% for textile to 1-15% for industrial and 100-500% for elastomeric fibers.

Fibers or filaments are converted into yarns by twisting or entangling processes that improve strength, abrasion resistance, and handling. Yarn properties depend on those of the fibers or filaments as well as on the angle of twist. Yarns are interlaced into fabrics by various mechanical processes, including weaving, knitting, and braiding. There are three prevalent fabric structures used for medical implants or sutures: woven, in which two sets of yarns are interlaced at right angles; knitted, in which loops of yarn are intermeshed; and braided, in which three or more yarns cross one another in a diagonal pattern. Knitted fabrics can be either weft or warp knit, and braided products can include tubular structures, with or without a core, as well as ribbon.

There are also numerous medical uses for nonwoven fabrics (wipes, sponges, dressings, gowns), made directly from fibers that are needle-felted, hydroentangled, or bonded through a thermal, chemical, or adhesive process. Nonwovens may also be made directly from a polymer. Expanded polytetrafluoroethylene (ePTFE) products such as sutures and arterial grafts and electrostatically spun polyurethane used as tubular structures are examples of medical applications of polymer-to-fabric nonwovens.

The properties of fabrics depend on the characteristics of the constituent yarns or fibers and on the geometry of the formed structure. Whether a fabric is woven, knitted, braided, or nonwoven will affect its behavior. Fabrics that are woven are usually dimensionally very stable but less extensible and porous than the other structures. One disadvantage of wovens is their tendency to unravel at the edges when cut squarely or obliquely for implantation. However, the stitching technique known as a Leno weave—in which two warp threads twist around a weft—an substantially alleviate this fraying or unraveling.

Compared with woven fabrics, weft-knitted structures are highly extensible, but they are also dimensionally unstable unless additional yarns are used to interlock the loops and reduce the extension while increasing elastic recovery. Warp-knitted structures are extremely versatile, and can be engineered with a variety of mechanical properties matching those of woven fabrics. The major advantage of knitted materials is their flexibility and inherent ability to resist unraveling when cut. A potential limitation of knitted fabrics is their high porosity, which—unlike that of woven fabrics—cannot be reduced below a certain value determined by the construction. As a result, applications requiring very low porosity usually incorporate woven materials.

Typically employed in cords and sutures, braided structures can be designed using several different patterns, either with or without a core. Because the yarns criss-cross each other, braided materials are usually porous and may imbibe fluids within the interstitial spaces between yarns or filaments. To reduce their capillarity, braided materials are often treated with a biodegradable (polylactic acid) or nonbiodegradable (Teflon®) coating. Such coatings also serve to reduce chatter or noise during body movement, improve hand or feel, and help position suture knots that must be transported by pressure from a surgeon's finger from outside the body to the wound itself.

The properties of nonwoven fabrics are determined by those of the constituent polymer or fiber and by the bonding process. For instance, expanded PTFE products can be formed to meet varying porosity requirements. Because of the expanded nature of their microstructure, these materials compress easily and then expand—a suture, for example, can expand to fill the needle hole made in a tissue—allowing for tissue ingrowth in applications such as arterial and patch grafts. Polyurethane-based nonwovens produce a product that resembles collagenous material in both structure and mechanical properties, particularly compliance (extension per unit pressure or stress). The porosity of both PTFE- and polyurethane-derived nonwovens can be effectively manipulated through control of the manufacturing processes.

In one embodiment of the invention, the tissue engaging element utilized in the implantable device is fabricated by warp knitting a monofilament polypropylene yarn that is approximately 3 to 6 mils in diameter. In one exemplary embodiment, the yarn is 3.5 mils in diameter. In this embodiment, the knitted mesh preferably has 40-80 courses per inch and 7-11 wales per inch. Other designs of medical textiles may also be used.

In addition to the polymeric fibers described above, non-polymeric fibers may be used in constructing woven, braided, knitted and non-woven fabrics for use in the invention. For example, nitinol or stainless steel fibers may be used alone or in combination with other fibers such as polymeric fibers to construct a tissue engaging element having altered retraction properties.

A perforated film-type product (not shown) may alternatively be used in fabricating the tissue engaging element. In that embodiment, a polymer film is perforated with a plurality of holes to engage tissue and to allow tissue ingrowth. The size and spacing of the holes may be optimized for those functions. Further, the size and spacing of the holes may be varied over the film to promote greater tissue engagement in certain locations on the film.

The tissue engaging element may comprise a film having other types of tissue engaging features, alone or in combination with perforations. For example, the film may comprise corrugations, dimples, knurling or other embossed, molded or machined relief patterns that engage tissue that is pressed against the tissue engaging element. Full or partial perforations may include raised edges that engage surrounding tissue.

A retracting element shown in FIG. 6 b, such as a flexible backing or arch 601, may be used. The retracting element 601 is fabricated from a biocompatible material such as stainless steel, nitinol, silicone, polyethylene, polytetrafluoroethylene, or polypropylene. The retracting element is preferably capable of withstanding a large number of flex cycles without fatigue failure because the element undergoes a strain cycle with each movement of the pharyngeal wall, such as in swallowing and speaking. The retracting element 601 may be produced with a three-dimensional geometry in order to exert specific directional forces when deployed that change one or more characteristics of the pharyngeal wall, as described in more detail below.

In another embodiment, the retracting element may be substantially non-flexible. A non-flexible retracting element may be fabricated from titanium, stainless steel or ceramic. An implantable device including a non-flexible retracting element may be used to maintain a shape of a pharyngeal wall to prevent collapse.

A retracting element 601 may be attached to a tissue engaging element 600, as shown in FIG. 6 c, in another embodiment of the invention. The attachment may be by adhesive, suture, clips, staples, screws, or another fastening means such as ultrasonic welding. As noted above, the tissue engaging element engages surrounding tissue after implantation and promotes tissue ingrowth, becoming permanently integrated with the surrounding tissue. As a result, the retracting element 601 becomes permanently fixed in position beneath the pharyngeal wall and will not migrate. The result is that the pharyngeal wall is less likely to collapse during sleep and produce an obstruction to breathing.

In an alternative embodiment of the invention, the tissue engaging element, the retracting element, or both can be at least partially fabricated from resorbable synthetic polymers such as polylactide, polyglactide, polydioxanone, polycaprolactone, or co-polymers thereof. The long-term shape of the soft tissue is provided through the presence of the tissue formed around and through the tissue engaging element as the absorbable component of the implant is resorbed.

FIGS. 6 d-6 f are cross-sectional views through several embodiments of a implantable device of the invention incorporating both a mesh tissue engaging element and an arch-shaped retracting element. FIG. 6 d is a cross-sectional view of the device of FIG. 6 c, wherein one side of the tissue engaging element 601 is attached to a retracting element 601. The tissue engaging element 601 may be attached through the use of adhesives, such as cyanoacrylates, silicones and hot melt polymers. The adhesives may be absorbable or non-absorbable. The tissue engaging element may alternatively be attached through the use of mechanical fixation means such as sutures and clips.

Alternatively, as shown in FIG. 6 e, the retracting element may be produced with a reduced width and then passed through or woven into the mesh component. The figure shows an embodiment wherein the flexible arch is encased within a sleeve 603 comprising the tissue engaging element. The retracting element may alternatively comprise holes, slots or other features (not shown) allowing the retracting element to be interwoven into the fabric of the tissue engaging element.

In the embodiment shown in FIG. 6 f, the mesh 600 is attached to two retracting elements 601 a and 601 b, one on each side of the mesh component. All of the embodiments shown may be used to provide sustained retraction or shaping of the pharyngeal wall.

Optionally, image-enhancing substances such as radio-opaque or ultrasonically sensitive materials can be layered onto any of the surfaces of the pharyngeal retractor to aid in imaging of the device during and after deployment. In another embodiment, anti-microbial agents such as triclosan or antibiotics, or pain management medicaments are applied or coated to one or more surfaces of the components that comprise the pharyngeal retractor prior to deployment. Alternatively, the agents may be included in the polymers during the fabrication processes through extrusion, blending, casting, solvent mixing or other typical polymer processing means. The agents may be included within an absorbable component to provide controlled or profiled release of the substances during wound healing.

Orientation of the implantable device in the patient may be selected depending on the particular patient anatomy. For example, an elongated device may be placed so that the device ends are in the same plane as the pharynx or in a plane parallel to the pharyngeal axis (PAX), as illustrated by the device 700 shown in FIG. 7; i.e., so that a longitudinal axis of the device is parallel to the pharyngeal axis. Alternatively, the mesh strip may be placed perpendicular to the pharyngeal axis (PAX), as illustrated by the device 800 shown in FIG. 8. In that case, the longitudinal axis of the mesh strip is perpendicular to the pharyngeal axis. In either case, the implantable device (with or without a retracting element) is placed by a surgeon in such a way so as to change the shape of the pharyngeal walls to prevent collapse during inhalation.

In addition to placing the implantable device using a trocar in a minimally invasive approach, the device of the invention may also be placed underneath the pharyngeal wall using an open, direct visualization approach to the pharynx from the side of a patient's neck. A similar approach to the tissue space underneath the pharyngeal wall is used to perform cervical spinal disc replacement. That approach may be used in the present invention on an outpatient basis or one night hospital stay, for example.

The implantable device of the invention may be a retractor 900 (FIG. 9) that is produced as or includes a fibrous element 905 with tissue engaging features 910. The tissue engaging features may be directional frictional features such as the barbs shown in the figure, or may be non-directional frictional features such as those of a textile. Fibrous elements 905 may be produced as a barbed monofilament, as a braided textile structure with frictional elements encased with the braid, as a combination barbed/braided structure, or as a textile or filament having a roughened or high-friction surface.

The view of FIG. 9 is a section through a patient's neck showing the tongue T, lower mandible M, skin S, posterior pharyngeal wall PPW and pharyngeal airway PA. The fibrous elements 905 are passed through the pharyngeal wall from within the oral cavity with the two ends of the elements 905 entering a single hole located medially on the lateral aspect of the pharyngeal wall. In the placement, the retractor 900 may be passed in an anterior/posterior orientation and exits the skin of the neck. A protective sheath similar to sheath 501 shown in FIG. 5 may be used to protect tissue during placement of the fibrous elements 905, particularly in the case where the tissue engaging element is a non-directional frictional feature. After placement, a central portion 930 of the retractor engages tissue beneath the pharyngeal wall. Needles 920 may be incorporated into the fibrous elements 905 to facilitate placement.

The fibrous elements 905 are tensioned to retract the pharyngeal wall by producing tension on tissue beneath the lateral pharyngeal wall, or a tenting effect of the lateral wall if the elements are placed with a slight posterior/lateral and anterior/lateral angle during passage. Once sufficient tension is applied, and the lateral wall is suspended, the ends of the fibrous elements 905 are trimmed flush with the surface of the skin S and are allowed to retract slightly to remain in a sub-dermal position. Alternatively, the retractor elements may be passed directly laterally to exit the lateral tissue of the neck of the patient to provide direct lateral suspension of the pharyngeal wall.

In another method of implantation, the pharyngeal retractors described above are implanted through an oral route. In its simplest embodiment, the method of implanting the device utilizes conventional surgical instruments such as a scalpel, forceps, etc with direct visualization of the pharyngeal wall though the mouth. Alternatively, the devices can be implanted using a hand-held delivery system. FIG. 10 illustrates the approach used to deliver one of the pharyngeal retractors previously illustrated in FIGS. 6 a-6 f. The hand-held delivery system 1000 comprises a hand-piece 1090, a shaft 1091 extending therefrom, and a housing 1092 on the distal end 1093 of the shaft 1091. The housing is capable of holding at least one of the pharyngeal retractors 1094. The pharyngeal retractors are held in the housing in a constrained configuration.

The pharyngeal retractors are advanced out of the delivery system by a deployment means actuated by a lever 1097 on the hand-piece 1090. As the pharyngeal retractors are advanced out of the housing, they are deployed through a previously made incision in either the posterior or the lateral pharyngeal wall. Alternatively, the distal-most portion of the delivery system may have a sharpened edge to facilitate penetration of the pharyngeal wall during deployment of the retractor 1094. The retractors can then be set beneath the pharyngeal walls to provide constant retraction of the airway.

FIGS. 11 a and 11 b illustrate the effect of implanting two of the devices of the invention to alter the shape of the pharyngeal airway. The distance between the left lateral pharyngeal surface and the right lateral surface is represented by distance A. The retractors 1120 are shown in FIG. 11 a in a constrained configuration, with a distance B between the ends of each retractor which is greater than the distance between the ends of the unconstrained retractor. The retractor is maintained in the constrained configuration with the tips 1121 a, 1121 b spread open within a delivery cannula or hollow stylus. The implantable device is passed into the tissues beneath the pharyngeal wall within a pre-defined arc of the cannula or hollow stylus.

Upon termination of the stylus advancement, the implantable device is ejected from the cannula or stylus by a pusher that maintains the implantable device in a fixed position while the cannula/stylus is withdrawn from the penetrated tissue beneath the pharyngeal wall. Effectively, the implantable device does not move; rather, the stylus is withdrawn from around the implantable device. After deployment, the implantable device returns to its unconstrained configuration with the tips 1121 a′, 1121 b′ of the retractors 1120′ contracting as shown in FIG. 11 b to the distance represented as B′, which is smaller than distance B.

When the implantable device is placed in position beneath the pharyngeal wall 1030, the tips 1121 a, 1121 b of the device engage the pharyngeal wall so that the wall changes shape as the distance B between the tips changes. For example, the tips may engage the pharyngeal wall by pinching a portion of the wall between them. In another example, the tips 1121 a, 1121 b may have barbs', hooks, roughening or another tissue engaging feature to maintain engagement of the tips with the pharyngeal wall to exert a force on the wall.

After deployment of the two devices, the distance A between the lateral pharyngeal walls increases to A′, and the shape of the airway is altered to produce two small irregular channels 1140, 1141 of decreased radius of curvature in the pharyngeal wall 1130 parallel to the axis of the airway. The geometry of the channels is sufficiently small to prevent the relaxed tongue from forming a seal with the pharyngeal wall along those locations while a patient is in a sleeping state and the musculature of the tongue relaxes. While the tongue may seal with the posterior pharyngeal wall, the lateral aspects are maintained as open channels 1140, 1141, effectively allowing air to flow past the obstruction.

In another embodiment of the invention shown in FIGS. 12 a and 12 b, two implantable devices 1220 are used to produce anterior-to-posterior retraction of the pharyngeal airway to alter the shape of the airway. The distance between the anterior pharyngeal wall surface and the posterior pharyngeal wall surface is shown in FIG. 12 a as distance B. Similar to the embodiment discussed in FIG. 11, the implantable devices are illustrated in FIG. 12 as deployed through the use of a deployment cannula or hollow stylus. The cannula or hollow stylus has a curved interior having an arch shape with a radius smaller than a radius of the implantable device in its free state. The device is essentially held in a constrained configuration within the cannula or stylus and is allowed to release during deployment. The ejection of the device from within the hollow cannula or stylus is again accomplished through the use of a pusher that maintains the device in a fixed position as the cannula is retracted.

During ejection, the radius of the implantable device increases and the distance between the tips of the device increases. Since the unconstrained devices 1220′ have a distance between the ends that is greater than the distance between ends of the constrained devices, the anterior-to-posterior dimension B of the pharyngeal airway increases to B′, thereby changing the shape of the airway by increasing the radius of curvature of the wall, as shown in FIG. 12 b. In this embodiment, the base of the tongue is also partially retracted from the edges of the tongue that abut the lateral location of the pharyngeal wall, the shape of which has been altered through the use of the implantable devices.

While the implantable devices illustrated in FIGS. 11 and 12 are shown in the space beneath each of the lateral pharyngeal wall positions, a single device 1320 may be placed beneath the posterior pharyngeal wall (PPW) in a concentric placement to the axis of the pharynx (PA), as shown in FIG. 13. In this position, the device alters the shape of both lateral pharyngeal walls (LLPW & RLPW), thereby increasing the cross sectional area of the airway. Various length devices are feasible depending upon the severity of the pharyngeal wall collapse during sleep. In the case of pharyngeal wall collapse in the wakeful state, the implantable device may be fabricated to expand upon insertion, similar to the retractor illustrated in FIG. 12, to provide additional retraction during the awake state.

The devices, systems and surgical methods described above provide simple, minimally invasive procedures that may potentially be performed on an outpatient basis. Results of the procedures are both immediate and long-term. The implanted devices do not impact the hyoid bone or soft palate, and are therefore less likely to affect swallowing or speech. The invention furthermore uses materials with a long-term history of biocompatibility.

The foregoing Detailed Description and accompanying figures are to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the Description of the Invention, but rather from the Claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention. 

What is claimed is:
 1. A system for altering a shape of a pharyngeal wall by implantation of a device in tissue beneath the pharyngeal wall, the system comprising: a unitary, sheet-like flexible retracting element having first and second ends and having a constrained configuration wherein the first and second ends are separated by a first distance and an unconstrained configuration wherein the first and second ends are separated by a second distance different from the first distance; a tissue engaging element connected to the retracting element, the tissue engaging element comprising features for engaging the tissue beneath the pharyngeal wall; a plastic trocar sleeve having a proximal end fixed to at least one of the retracting element ends and tissue engaging element; and a trocar having a distal end, the plastic trocar sleeve attached to at least a portion of the distal end of the trocar, the trocar having a shape for positioning the retracting element and tissue engaging element in the tissue beneath the pharyngeal wall with the retracting element in the constrained configuration, and for releasing the retracting element to revert to the unconstrained configuration upon release, whereby a shape of the pharyngeal wall is altered when the retracting element reverts upon release from the trocar from the constrained configuration to the unconstrained configuration.
 2. The system of claim 1, further comprising: a sheath covering at least a portion of the tissue engaging element for protecting non-target tissue as the device is implanted.
 3. The system of claim 1, wherein the tissue engaging element comprises a material selected from the group consisting of a medical textile and a perforated sheet.
 4. The system of claim 1, wherein the tissue engaging element comprises a tissue engaging feature selected from the group consisting of a barb, a projection, a velour and a hook element.
 5. The system of claim 1, wherein the retracting element is comprised of a metal selected from the group consisting of nitinol, stainless steel, tantalum and titanium.
 6. The system of claim 1, wherein the retracting element comprises a flexible arch.
 7. The system of claim 1, wherein the retracting element and the tissue engaging element are attached using an attachment selected from the group consisting of adhesives, sutures, clips, rivets, interweaving and enveloping.
 8. The system of claim 1, further comprising: an image enhancing substance applied to the device, the substance selected from the group consisting of a radio-opaque substance and an echogenic substance.
 9. The system of claim 1, further comprising: a medicament applied to the device, the medicament selected from the group consisting of an anti-microbial, analgesic, anti-biotic, anti-inflammatory, and anti-pain medicament.
 10. A method for surgically treating obstructive sleep apnea, the method comprising the steps of: delivering an implantable device having first and second ends into tissue located beneath a pharyngeal wall, including introducing the implantable device orally and through the pharyngeal wall into the tissue beneath the pharyngeal wall, further including positioning a distal end of a hand-held delivery system proximate the pharyngeal wall, the hand-held delivery system containing at least one implantable device in a constrained state wherein the first and second ends are separated by a first distance; actuating a lever of the hand-held delivery system to advance the implantable device and a delivery element of the hand-held delivery system into the tissue beneath the pharyngeal wall; and maintaining the implantable device in a fixed position with a pusher while withdrawing the delivery element from a proximity of the implantable device, the implantable device assuming an unconstrained state wherein the first and second ends are separated by a second distance different from the first distance; and engaging the tissue beneath the pharyngeal wall with the implantable device to alter a shape of the pharyngeal wall.
 11. The method of claim 10, further comprising the step of: making one or more incisions in the pharyngeal wall.
 12. The method of claim 10, further comprising the step of: changing a radius of curvature of a portion of the pharyngeal wall.
 13. The method of claim 10, further comprising the step of: inducing tissue ingrowth into the implantable device.
 14. The method of claim 10, wherein the delivering step further comprises the steps of: penetrating the pharyngeal wall with the delivery element; and manipulating the delivery element to deliver the device into the tissue beneath the pharyngeal wall.
 15. The method of claim 10, wherein the implantable device includes a protective sheath surrounding at least a portion of the device; the method further comprising the step of: removing the sheath to permit the implantable device to engage the tissue beneath the pharyngeal wall.
 16. A system for treating obstructive sleep apnea by altering a shape of a pharyngeal wall, the system comprising: an implantable device having first and second ends and comprising a tissue engaging element and a unitary, sheet-like flexible retracting element; and a hand-held delivery system comprising a hand-piece, an actuating lever moveably connected to the hand-piece, a shaft extending distally from the hand-piece, a housing disposed at a distal end of the shaft and storing the implantable device, and a deployment device activatable by the lever for deploying the implantable device through the pharyngeal wall into tissue space located beneath the pharyngeal wall so as to alter a shape of the pharyngeal wall; the deployment device comprising a pusher for maintaining the implantable device in a fixed position and a delivery element proximate the implantable device, the delivery element being capable of withdrawal away from the implantable device to deploy the implantable device; wherein the implantable device has a constrained state in which the implantable device is flexed and the first and second ends are separated by a first distance, and an unconstrained state in which the implantable device is not flexed and the first and second ends are separated by a second distance different from the first distance, the unconstrained state having a different shape from the constrained state; and wherein the housing disposed at the distal end of the shaft stores the at least one implantable device in the constrained state, and the at least one implantable device reverts to the unconstrained state upon the deploying.
 17. The system of claim 16, wherein the implantable device comprises an arch-shaped member.
 18. The system of claim 16, wherein the distal end of the hand-held delivery system further comprises: a sharp edge for creating an incision in the pharyngeal wall through which the implantable device is deployed. 